    SCACHE(8)                                                            SCACHE(8)

    NAME
           scache - Postfix shared connection cache server

    SYNOPSIS
           scache [generic Postfix daemon options]

    DESCRIPTION
           The  scache(8)  server maintains a shared multi-connection
           cache. This information can be used by, for example, Post-
           fix SMTP clients or other Postfix delivery agents.

           The connection cache is organized into logical destination
           names, physical endpoint names, and connections.

           As a specific example, logical SMTP  destinations  specify
           (transport,  domain,  port),  and  physical SMTP endpoints
           specify (transport, IP address, port).  An SMTP connection
           may be saved after a successful mail transaction.

           In  the general case, one logical destination may refer to
           zero or more physical endpoints, one physical endpoint may
           be  referenced  by  zero or more logical destinations, and
           one endpoint may refer to zero or more connections.

           The exact syntax of a logical destination or endpoint name
           is  application  dependent;  the scache(8) server does not
           care.   A  connection  is  stored  as  a  file  descriptor
           together  with  application-dependent  information that is
           needed to re-activate  a  connection  object.  Again,  the
           scache(8)  server  is completely unaware of the details of
           that information.

           All information is stored  with  a  finite  time  to  live
           (ttl).   The  connection  cache  daemon terminates when no
           client is connected for max_idle time units.

           This server implements the following requests:

           save_endp ttl endpoint endpoint_properties file_descriptor
                  Save the specified file descriptor  and  connection
                  property  data  under  the specified endpoint name.
                  The endpoint properties are used by the  client  to
                  re-activate a passivated connection object.

           find_endp endpoint
                  Look   up  cached  properties  and  a  cached  file
                  descriptor for the specified endpoint.

           save_dest ttl destination destination_properties endpoint
                  Save the binding between a logical destination  and
                  an  endpoint  under  the destination name, together
                  with destination  specific  connection  properties.
                  The  destination  properties are used by the client
                  to re-activate a passivated connection object.

           find_dest destination
                  Look up cached destination properties, cached  end-
                  point  properties, and a cached file descriptor for
                  the specified logical destination.

    SECURITY
           The scache(8) server is not  security-sensitive.  It  does
           not  talk  to  the  network, and it does not talk to local
           users.  The scache(8) server can run chrooted at fixed low
           privilege.

           The scache(8) server is not a trusted process. It must not
           be used to store information that is security sensitive.

    DIAGNOSTICS
           Problems and transactions are logged to syslogd(8).

    BUGS
           The  session  cache  cannot  be  shared   among   multiple
           machines.

           When  a  connection  expires  from the cache, it is closed
           without the appropriate protocol specific handshake.

    CONFIGURATION PARAMETERS
           Changes  to  main.cf  are  picked  up   automatically   as
           scache(8) processes run for only a limited amount of time.
           Use the command "postfix reload" to speed up a change.

           The text below provides  only  a  parameter  summary.  See
           postconf(5) for more details including examples.

    RESOURCE CONTROLS
           connection_cache_ttl_limit (2s)
                  The  maximal  time-to-live value that the scache(8)
                  connection cache server allows.

           connection_cache_status_update_time (600s)
                  How frequently the scache(8) server logs usage sta-
                  tistics  with  connection  cache hit and miss rates
                  for logical  destinations  and  for  physical  end-
                  points.

    MISCELLANEOUS CONTROLS
           config_directory (see 'postconf -d' output)
                  The  default  location  of  the Postfix main.cf and
                  master.cf configuration files.

           daemon_timeout (18000s)
                  How much time a Postfix daemon process may take  to
                  handle  a  request  before  it  is  terminated by a
                  built-in watchdog timer.

           ipc_timeout (3600s)
                  The time limit for sending or receiving information
                  over an internal communication channel.

           max_idle (100s)
                  The  maximum  amount  of  time that an idle Postfix
                  daemon process waits  for  an  incoming  connection
                  before terminating voluntarily.

           process_id (read-only)
                  The  process  ID  of  a  Postfix  command or daemon
                  process.

           process_name (read-only)
                  The process name of a  Postfix  command  or  daemon
                  process.

           syslog_facility (mail)
                  The syslog facility of Postfix logging.

           syslog_name (see 'postconf -d' output)
                  The  mail  system  name  that  is  prepended to the
                  process name in syslog  records,  so  that  "smtpd"
                  becomes, for example, "postfix/smtpd".

    SEE ALSO
           smtp(8), SMTP client
           postconf(5), configuration parameters
           master(8), process manager
           syslogd(8), system logging

    README FILES
           CONNECTION_CACHE_README, Postfix connection cache

    LICENSE
           The Secure Mailer license must be  distributed  with  this
           software.

    HISTORY
           This service was introduced with Postfix version 2.2.

    AUTHOR(S)
           Wietse Venema
           IBM T.J. Watson Research
           P.O. Box 704
           Yorktown Heights, NY 10598, USA

                                                                         SCACHE(8)